This is very easy. The difficult part is protecting your ripper and your sewing machine from the thick fabric.
The lucky pair of jeans that I reconstructed was this:

I bought this more than five years ago. It’s large not because I lost weight. It doesn’t fit me well because when I was still an undergrad I had no idea how to buy a pair of jeans that hugged my legs in all the right places.
TUTORIAL
1. Measure your skirt length. 
2. Cut. Do not forget hem allowances. 
3. Once you cut the two legs, you will have something that looks like this:
4. Rip the inseam. This would be the seam that starts from the crotch. If you’re reconstructing heavy denim (this one is canvass-like), you may use cutter for ripping. I have heard stories of people breaking their rippers while doing this project. Just be very careful. 
5. Once you’re done ripping both inseams, you will have something that looks like this:
6. Now rip the seam all the way to the bottom of the front zipper. Do the same to the back side. Make sure to rip all the way to the butt area. 
8. At this point, you will have something similar to this:
10. Pin the parts you ripped apart. Front leg to the other front leg. Back leg to the other back leg. Your skirt will be recognizable at this point. Sew and hem. Make sure that the front part is flat and not bunchy when you sew the legs together. You might need to patch (with fabric taken from the pant legs you cut off) this part so that you’ll have a flat area.
AND YOU’RE DONE!
And here is my skirt. The color is a bit faded because I took these this morning while the tutorial pics were taken last night.
FRONT

SIDE

BACK

Thanks for looking and happy sewing!

Aug 27, 2007 @ 21:10:19
This skirt rocks! Thanks so much for the tutorial!
Aug 28, 2007 @ 15:33:16
nice!!!
(although mine would have to be a tad longer!!! my legs are not like yours…)
Aug 28, 2007 @ 17:59:00
Nicely done!
Aug 28, 2007 @ 17:59:56
Well, my legs…Must be a camera trick (although I did not edit them pics) because they never look that good in front of the mirror. tsk tsk
Aug 30, 2007 @ 00:27:12
Girls envy the asssssssssssssssssssssssssssssssss.
Sep 03, 2007 @ 01:59:41
Fabulous idea!
Apr 18, 2008 @ 00:25:57
You are so talented, i must sign up.
May 04, 2008 @ 00:50:43
now, this one is also great!!!..gonna try this..
thanks for this, Yam!..
pwede ko laag sa inyo? pa-tutor ko sewing and cutting..i’m serious! ^_^
May 09, 2008 @ 14:48:47
thanks! i just said a few days ago that i needed more skirts for the summer. i made a couple of quick & easy t-shirt mod skirts the other day, but i’d totally forgotten about this idea. i KNOW i’ve got old pants i can use for this.
Jul 24, 2008 @ 04:43:32
Wow thats pretty im 13 and i guess i can sew well. i might try that ONE day llol
Dec 02, 2008 @ 11:12:50
nice;) really nice;p
Moi and my skirt « Celina’s Photoblog
Jan 03, 2009 @ 15:26:00
[...] cut, ripped, and then sewed this skirt, basing off of this tutorial. I didn’t go step by step, just got the basic idea of ripping and cutting, then [...]
Feb 13, 2009 @ 19:09:31
Congratulations
¿ Can I post this work in mi blog?
I only will put one photo and the conection to your blog
Mar 14, 2009 @ 20:24:22
I have to say, that I can not agree with you in 100%, but it’s just my IMHO, which could be very wrong.
p.s. You have an awesome template . Where did you find it?
Sep 07, 2009 @ 08:22:29
love your tutorials. my daughter took piano lessons when she was a young girl, and i think she would like the piano bag. You have a way of making these tutorials very easy to understand and that’s what keeps my interest. look forward to trying your tutorials on the piano and guitar.
Sep 07, 2009 @ 13:38:36
Happy sewing! Hope your daughter loves the piano bag :)
Sep 07, 2009 @ 08:28:32
piano and guitar bags.
Sep 21, 2010 @ 22:10:18
wow great job. :)
Nov 06, 2010 @ 11:24:23
i have so much jeans back at home and i brought a few pair in manila to check out what to do since they are just there sitting in the cabinet. these are nice ideas to try! i hope i can do something as fabulous as this :) very inspiring!
Nov 09, 2010 @ 22:59:02
Happy sewing! :)